For example, US Patent Application Publication 2010/111317A1 and Japanese Patent Application Laid-open No. H05-333878 discloses a noise reduction device in which a plurality of microphones are arranged around an adjustable (reclinable) seat and a control sound for reducing the noise collected by the microphone is outputted from the speaker. US Patent Application Publication 2017/186417A1 also discloses a technique in which the choice to use/nonuse of a plurality of microphones and speakers is made depending on whether the seat headrest is above or below the center.